1. Field of the Invention
The present invention relates to a wide-angle zoom lens system which has a large-angle-of-view at the short focal length extremity, and which is suitable for a photographing lens system in a camera or a movie camera, etc.
2. Description of the Prior Art
In the prior art, as a zoom lens system attempting to achieve a wider angle-of-view at the short focal length extremity, such a zoom lens system has been disclosed, for example, in Japanese Unexamined Patent Publication (hereinafter, JUPP) No.2000-131611. However, in JUPP No. 2000-131611, the half angle-of-view at the short focal length extremity is 48γ, so that the wide angle-of-view is not sufficiently achieved at the short focal length extremity.
Furthermore, in JUPP No.2002-242336, proposed by the inventor of the present invention, the angle-of-view at the short focal length extremity has been made wider than that of JUPP No. 2000-131611; however, the zoom ratio is approximately 2. Therefore a higher zoom ratio has yet been required.
Still further, in the case of a wide-angle zoom lens system of a five-lens-group arrangement like the zoom lens system of the present invention, such a wide-angle zoom lens system has been proposed in, e.g., JUPP Nos. Hei-7-306362, Hei-9-0.230242, and 2000-292701.
In JUPP No. Hei-7-306362, the zoom ratio is as high as 3.75; however, the angle-of-view at the short focal length extremity is not sufficiently larger.
In JUPP No. Hei-9-230242, the zoom ratio is 2.75, which is also high; however, the angle-of-view at the short focal length extremity is not sufficiently larger.
The zoom lens system, disclosed in JUPP No. 2000-292701, is to be used in a projector; and the angle-of-view at the short focal length extremity is not sufficiently larger. Moreover, the overall length of the zoom lens system is fixed (not variable), and is not suitable for a photographing lens to which miniaturization is required for portability.